Wet conditions in the Wimmera, coupled with an optimistic outlook for spring, have prompted inquiries into the use of plant growth regulators (PGRs) on barley to minimise lodging and crop head loss.
In seasons with high yield potential, the risk of barley yield loss increases, due to the development of heavy heads relative to plant height and stem strength.
Tall barley varieties such as Compass and Scope CL are particularly susceptible.
PGRs inhibit the plant’s synthesis of gibberellin, a plant hormone that regulates growth and influences stem elongation.
When gibberellin production is limited, stem growth is retarded and the stem wall thickness increased.
Field research carried out by BCG and Agritech Rural in the Wimmera in 2013 and 2014 showed that PGRs can improve crop yields, but only in seasons that are conducive to high biomass production and yield potential.
In 2013, when 341mm of growing season rainfall was received, PGRs applied at 400ml/ha at growth stage 31 and 39 had a positive effect on wheat yield.
Conversely, at Horsham in 2014, when growing season rainfall was just 172mm, PGRs were not economically viable or worthwhile.
This was likely due to crop stalks being strong enough to support smaller grain heads.
According to BCG researcher Kelly Angel, these results are in line with recommendations and research which suggests that Moddus Evo – recently registered for use on wheat, barley and oats – and other PGRs need to be tailored to seasonal conditions. “If growing conditions are less than ideal and the crop is suffering environmental stresses, such as frost and lack of moisture, the risk of crop damage may outweigh the benefits of applying a PGR,” she said.
Ms Angel said that PGRs still had an unknown place in the Wimmera’s farming systems.
“While there is evidence to suggest that there are seasons where PGRs may deliver good results, there are also results which show that in poorer seasons their use may be both uneconomical and risky to crop production,” she said.
“Paddock, crop variety and season outlook all play a part in the decision-making process.”
BCG has established field trials at Kalkee, examining their use on LaTrobe and Compass barley and on Yallara and Wintaroo oats.
